Field
The present disclosure relates to network management. More specifically, the present disclosure relates to layer-3 overlays in a network.
Related Art
The exponential growth of the Internet has made it a popular delivery medium for a variety of applications running on physical and virtual devices. Such applications have brought with them an increasing demand for bandwidth. As a result, equipment vendors race to build larger and faster switches with versatile capabilities, such as awareness of virtual machine migration, to move more traffic efficiently. However, the size of a switch cannot grow infinitely. It is limited by physical space, power consumption, and design complexity, to name a few factors. Furthermore, switches with higher capability are usually more complex and expensive. More importantly, because an overly large and complex system often does not provide economy of scale, simply increasing the size and capability of a switch may prove economically unviable due to the increased per-port cost.
As Internet traffic is becoming more diverse, virtual computing in a network is becoming progressively more important as a value proposition for network architects. The evolution of virtual computing has placed additional requirements on the network. However, conventional layer-2 network architecture often cannot readily accommodate the dynamic nature of virtual machines. For example, in conventional datacenter architecture, host machines can be inter-connected by layer-2 (e.g., Ethernet) interconnects forming a layer-2 broadcast domain. Because of the physical reach limitation of a layer-2 broadcast domain, a datacenter is typically segmented into different layer-2 broadcast domains. Consequently, any communication to outside of a layer-2 broadcast domain is carried over layer-3 networks. As the locations of virtual machines become more mobile and dynamic, and data communication from the virtual machine becomes more diverse, it is often desirable that the network infrastructure can provide layer-3 network overlay tunnels to assist the data communication acrosslayer-2 broadcast domains.
While overlays bring many desirable features to a network, some issues remain unsolved in providing a logical subnet across layer-2 broadcast domains.